It is the aim of the present Phase II research program to develop a continuous, noninvasive, on-line process for optically monitoring the levels of urea in a patient's blood during hemodialysis. The ultimate goal of such a process is to provide a direct and continuous measure of the efficiency of dialysis without having to wait for the drawing of a blood sample, thereby providing an assessment of whether dialysis at any point in time has reached an effective stopping point for the patient while still attached to the dialysis equipment. We propose to utilize low-resolution laser Raman scattering for the direct measurement of the urea levels in blood using the optical access provided by the dialysis tubing delivering the patient's blood to the dialyzer. Our Phase I SBIR results have shown that urea has a unique Raman spectroscopic signature in animal blood and can be identified and quantified against a whole blood background. Our Phase II program is designed to assess the capability of Raman to quantify the levels of urea in human blood samples with varying concentrations of urea present. After constructing a suitable multiple regression model for BUN, we will build out an appropriate low-resolution Raman module for attachment to a hemodialysis unit and expand the investigation to human blood analysis for BUN and URR during actual dialysis procedures in the clinical setting. If successful, a Raman measurement approach would allow, for the first time, real-time, direct and continuous monitoring of the progress of urea removal dudng the course of hemodialysis. This would permit more efficient timing of the dialysis procedure for the patient, as well as providing an ongoing readout of the effectiveness of the dialysis system during patient treatment. We anticipate that a commercially viable urea monitor might be produced rapidly, if the Phase II work is successful, by the adaptation for the clinical setting of the Company's present R-2001 Raman module for attachment by fiberoptic probe to existing renal dialysis equipment.